1. Field of the Invention
This invention relates generally to the field of aerosol sprays and specifically to an agitator for a spray paint can.
2. Description of Related Art
A spray can typically contains a mixture of solid particles, such as a pigment, suspended in a liquid vehicle which may include resins, oils and solvents to be sprayed from the can toward some object. Commonly this mixture is paint used to cover and color an object. Also contained in the can is a propellant which is usually a liquified gas, such as butane, propane, or isobutane, contained under pressure in the can. When a valve on the can is opened, the propellant forces the paint from the can and the paint is directed toward the object being sprayed.
If the can remains relatively motionless for any length of time, the pigment tends to settle to the bottom of the can. To assure that the pigment is efficiently removed from the can and sprayed on the object, it is necessary to mix the pigment with the vehicle by some means of agitation.
To achieve mixing, it is possible to merely shake the can, however, when the pigment is dense or cohesive, mixing will generally be inadequate. It has long been known to use a spherical ball as an agitator inside the can to move through and mix the contents when the can is shaken. Such agitator balls remain in use today. However, it has been found that a substantial portion of the pigment is trapped in the corner formed by the side and bottom of the can. The standard spherical agitator, because of its shape, cannot reach into the corner to mix the contents. Moreover, the corners in such cans are made more difficult to access because the pressurized contents of the can require a domed bottom which results in an acute angle at the corner. A smaller ball used as an agitator will tend to stick in the pigment at the corners because of its smaller mass, and therefore, is ineffective.
U.S. Pat. No. 3,087,707 to Moonan shows an agitation means which includes a standard spherical ball and, in addition, several smaller spherical balls. The smaller balls mix the pigment from the corners. The large ball serves the normal agitation function and is also able to dislodge smaller balls which become stuck. This requires a multiplicity of members carefully sized according to the dimensions of the can, so that the small balls can move into the corner and the large ball can dislodge the small balls without itself becoming stuck.
Another type of agitator is a device shown in U.S. Pat. No. 17 2,580,132 to Seymour which resembles a pair of tombstones joined at their bases at an obtuse angle. The Seymour agitator, however, has flat sides with sharp corners which would tend to become stuck in a thick solution.
Uniform spherical balls have remained in use as agitators while the search for a simple and effective agitator has continued.